Standards for fuses in the United States provide for different interrupting capacity fuses having generally the same exterior dimensions, specifically length and diameter. In such cases it is the practice to provide a rejection feature in both the fuses and the fuse blocks such that in the case of like dimension fuses, those having a lower interrupting capacity are prevented from being inserted in a fuse block specifically designed for those having a higher interrupting capacity. For example, one form of rejection feature well known in the art is to use ferrule-type fuses with an annular groove in the ferrule at one end of the fuse. Various fuse blocks are known in the art which will accept a fuse of predetermined higher interrupting capacity but will reject a fuse of like dimension but of lower interrupting capacity. Examples of this type of fuse block are disclosed in U.S. Pat. Nos. 4,257,662 to Matten, 4,097,114 to Matten, 3,960,435 to Bailey et al. and 4,178,063 to Reynolds.
Another form of rejection feature is provided for Class CC fuses in which one end of a fuse is configured with a ferrule having a concentric cap of lesser dimension than the ferrule. A fuse having this form of rejection feature and a fuse clip for accepting fuses with this feature while rejecting other tpes of fuses are disclosed in U.S. Pat. No. 3,585,558 to Swain which teaches the use of a fuse block having a pair of spaced fuse clips with rejection abutments. Also of interest is the Underwriters Laboratory standard for Class CC Fuseholder Ferrule Contact-Type Rejection Member, UL 512, as described at page 8D therein. In accordance with the Underwriters Laboratory standard a fuse clip with end stops is used in combination with a rejection stop and terminal. A disadvantage of both the Swain and Underwriters Laboratory arrangements is that the dimensional tolerance of the overall length of the fuse and the fuse block must be carefully controlled. A further disadvantage of the Swain arrangement is that while it prevents the insertion of the incorrect fuse, it allows electrical contact during an attempt to insert an incorrect fuse.